The night was quiet, but not empty.
Ren Aoki opened his eyes slowly, eyelids heavy, the faint taste of ash in his mouth.
The cold, rough floor pressed against his palms.
Dust drifted lazily in the pale moonlight leaking through gaps in the broken roof. For a moment, he thought he might still be dreaming.
But the ache in his arms, the sting along his ribs, the faint warmth of blood on his fingers—all told him otherwise.
"…Where… am I?" His voice was barely audible.
Shadows shifted around him. Broken pillars leaned precariously, charred beams sagged under the weight of destruction, and faint embers glowed here and there. The remnants of a once-grand mansion lay in ruin.
Ren's mind felt foggy at first. Then flashes came—quick, sharp, like shards of glass.
A narrow room. Screens glowing in the dark. A life lived quietly, unnoticed.
A grand hall. Servants bowing. A strict man's sharp gaze. A woman's gentle smile.
A name. Ren Aoki.
He clenched his fists instinctively. "…Who am I?"
Two lives tangled in his head. One was the lonely boy from another world; the other, the young master of this burned estate.
He closed his eyes. When he opened them again, his gaze had sharpened. Calm. Determined.
"I see."
The words were soft, but felt deliberate. "…I'm Ren Aoki."
A faint wind whispered through the ruins. Ash swirled across the floor.
Then memory stabbed through the haze:
The screams. Blood. Fire.
A figure—pale, grinning, almost human in shape—but wrong, all wrong.
Ren's chest tightened. "…So that wasn't a dream."
He lowered his head, silent. Not crying. Not panicked. Just… absorbing the impossibility of it all.
Another memory rose—one less terrifying, but no less significant: a man in a dark uniform, sword in hand, calm voice cutting through chaos.
"You're the only survivor."
Ren exhaled slowly. "…Saved by a Demon Slayer."
He looked up at the fractured roof. The moonlight caught fragments of glass and ash. His lips twitched in what might have been the faintest hint of humor.
Demon Slayer… great. Just what I wanted. Couldn't I have ended up in some peaceful place instead?
His eyes scanned the ruins. Broken beams, jagged walls, shadows thick in the corners. The faint scent of blood still lingered, mixed with smoke and damp wood.
A soft, mechanical voice echoed in his mind.
[Techno Genesis System — basic module connected.]
Ren blinked, unfazed. "…System?"
No light. No miraculous surge of energy. Just a subtle awareness, like a program running quietly in the background.
[Basic support functions available.]
[Advanced modules locked.]
Ren exhaled softly. "…So I really did get isekai'd."
Another thought, faintly sarcastic, crept in:
Couldn't I at least wake up somewhere warm? Somewhere safe? No… gotta be in charred ruins at night. Lovely.
He pushed himself to his feet. The cold air of the night brushed against his skin. His small frame looked fragile, almost delicate—fragile enough to seem like he shouldn't survive in this cruel world.
But his gaze was steady, his movements deliberate.
"…Fine," he murmured. "…If demons exist in this world, then I'll deal with them in my own way."
From the shadowed edge of the forest beyond the mansion, something stirred.
A low growl rumbled through the darkness.
Eyes glinted. Teeth flashed. Muscles tensed instinctively.
A demon—low-tier, a minion, likely injured by a previous encounter with a core member—had sensed movement. Its instincts screamed, but its body betrayed it. Weak, sluggish, regeneration slowed.
It was the perfect opening.
Ren crouched behind a broken beam, watching. Every twitch of its limbs, every shift in balance, every flick of its claws gave him information.
The demon lunged, claws swiping through the air. Ren rolled aside, letting the strike miss by inches. His small frame pressed against shadowed rubble, moving almost like a ghost through moonlight and ash.
He scanned the ruins. Ash, splintered wood, fallen furniture. Every piece could be a tool, a distraction, a weapon if used cleverly.
The demon circled, growling low. Its movements were instinct-driven, yet dangerous. It hissed at him, aware now, sharp eyes glinting in the moonlight.
Ren's lips twitched with faint humor. Maybe I can make it trip on debris. Or run into a wall. Could be fun… or dumb. Either works.
He ignored the thought. Observation mattered more than jokes.
Then, a glint caught his eye.
A sword. Partially buried under rubble. The design unmistakable—a fallen Demon Slayer core member's weapon, engraved faintly with ceremonial marks.
Ren froze for a heartbeat. The weight, the balance, the potential—it was perfect.
He crept forward, careful not to alert the demon. It twitched, sensing motion, but sluggishly—its injuries slowed reflexes.
Ren's fingers wrapped around the hilt. Solid. Familiar in shape, though unpracticed in his hands. He could feel leverage, balance, timing.
The demon lunged again. Ren sidestepped instinctively, swinging the sword with careful precision. The blade cut across its arm, leaving a shallow gash. Not lethal—but enough to test.
The demon screamed, stumbling back, claws swiping blindly. Ren rolled, adjusted his stance, swung again. Deeper now. The creature faltered, twitching.
Weak minion… lucky for me.
But he didn't relax. Even injured, sluggish, and low-tier, it was still dangerous.
Ren exhaled softly. Not dead. Not strong. Not dangerous… for now.
He crouched in shadow, thinking. The fight had been won not by strength, but by clever timing and seizing an opportunity.
The moonlight shifted. Shadows moved. Somewhere deeper in the ruins, higher-ranking demons waited. Watching. Sending minions. Observing the world that humans still believed they controlled.
Ren adjusted his grip on the sword. His pale hands gleamed in the dim light. Calm, measured, yet aware of danger.
Observation, patience… that's enough for now.
And somewhere, in the darkness, a new presence stirred. A higher-ranked demon, silent, observing, waiting for its chance.
Not yet a threat—but soon.
Ren exhaled again. His face flushed faintly at the thought of someone noticing him—someone human, someone else—but quickly he shoved the blush aside. No one was here now. Only the ruins, the ash, and the faint cries of a low-tier demon minion, subdued but alive.
I'll need to get stronger. Smarter. Faster. Every fight from now on… will be like this.
The night stretched on. Silent. Cold. Dangerous.
Ren Aoki stepped carefully through the ruins, sword in hand, mind sharp, ready for what came next.
The first night had passed—but the real danger had only begun.
***
The night air was sharp, scented with smoke and cold earth.
Ren's bare feet pressed against the damp ground as he stepped out of the ruins.
Broken pillars and charred wood lay scattered around him, and the moonlight painted jagged shadows across the forest edge.
Somewhere in the distance, the faint rustle of leaves hinted that he was not alone.
He adjusted the grip on the core member's sword, the hilt pressing lightly into his small hands. The blade's weight was reassuring—not heavy, not cumbersome—but enough to make him feel like he belonged here, even for a fleeting moment.
Ren paused, listening. The forest was alive with sounds: the snap of a branch under some small animal, the whisper of wind through trees, the faint dripping of water from broken beams and leaves.
Somewhere deeper, a demon stirred. He could feel its presence rather than see it, a subtle disturbance in the natural rhythm of the night.
They are predators, he thought quietly. But they have patterns. They have weaknesses.
He crept forward, shadow to shadow, careful to avoid open ground.
The ruins had been one thing—predictable in their chaos—but the forest was another. Here, the moonlight penetrated in shafts between trees, illuminating patches of undergrowth, exposing both advantage and danger.
A low growl broke the quiet.
Ren froze.
Ahead, crouched beneath a cluster of dense ferns, a demon was moving. Small, humanoid, but unmistakably wrong—the skin pallid, eyes glinting unnaturally, claws scraping against bark.
It was not the same as the minion he had fought in the ruins. This one seemed younger, newly formed, almost naive, yet its instincts screamed hostility.
Ren inhaled slowly, letting the tension build in his chest. He stepped lightly, testing his footing on fallen leaves and dry branches. One snap would give him away.
Newly made, probably not fully fed. But still lethal enough if I slip.
The demon froze, sniffing the air. Its eyes found him, wide and unblinking. It hissed, a sound that made the hairs on Ren's neck rise.
He crouched lower, sword raised slightly, ready.
The first lunge was swift, but crude. The demon's injuries from some prior encounter—he guessed with a stronger demon—made its movements uneven. It clawed blindly, swiping too wide, too slow. Ren rolled aside, feeling a brush of its hand against his sleeve.
He let it strike, then studied the angles.
Each motion told him something: balance, preferred attack, hesitation.
So, it's not a core-level threat. It's cautious, but not smart.
Ren pressed forward, moving silently through the shadows. He drew the sword back and sliced across the demon's side, a shallow cut that didn't kill but startled it. The creature hissed and recoiled, its regeneration already sluggish from prior injury.
Ren's lips twitched faintly. If only it were brighter… oh well.
The demon lunged again, faster this time, claw aimed at his chest. Ren ducked, letting the attack pass over. A faint beam of moonlight caught the blade of his sword. He shifted his angle, stepping closer to the tree cover.
Then he noticed something—a patch of disturbed earth near a fallen log.
Ren crouched low, hiding from the demon's gaze. Buried partially under the soil and debris was another weapon: a small dagger, perhaps dropped by a human before a sudden attack. Its blade was short, almost ornamental, but sharp.
Not bad… could be useful.
The demon hissed again, impatient. It didn't understand the advantage Ren had found.
Its movements were jerky, overcompensating for injuries, but still lethal enough to make any mistake fatal.
Ren stepped forward, angling himself between the moonlight and shadows, letting the forest obscure him while he readied the dagger in his free hand. He didn't think of himself as clever. He didn't dwell on strategy in words. He moved, and the choices he made revealed it naturally.
A feint here, a roll there, a low slice of the dagger, a push with the sword. The demon's balance faltered. Its claws flailed. It shrieked, a raw, inhuman sound that echoed through the trees.
And then, just as it lunged blindly, Ren pressed his advantage. A swift, precise strike with the core sword connected with its neck. The creature froze, its limbs twitching once before it collapsed into the damp leaves.
Ren exhaled. The forest returned to quiet, save for distant animal noises and the faint rustle of wind through the trees.
He lowered the sword slightly, feeling the faintest flush on his cheeks—not embarrassment, exactly, but the heat of exertion and relief. Even in isolation, he was aware of his own fragility, of how small he looked compared to the dangers lurking in the dark.
He pressed on, moving deeper into the forest. Each step was cautious, each shadow a potential threat. Yet, he felt a strange sense of calm—the kind that comes when you survive a fight without relying on brute strength, when observation and timing are your only allies.
Somewhere in the distance, higher-ranked demons moved silently among the trees, watching, waiting, sending low-tier minions to test intruders.
Ren did not notice them yet. He did not need to. The night was long, and the forest held many secrets, each more dangerous than the last.
But he had survived this far. And that was enough—for now.
The moon traced pale paths across the ground, illuminating patches of moss and broken branches. Ren paused, brushing dirt from his hands, eyes reflecting the faint glow of moonlight.
I will need to understand this world. To move through it without being destroyed.
A rustle of leaves behind him made him spin, sword raised, but it was only a small animal, scurrying away in panic. His lips twitched faintly again, almost a laugh.
Better safe than dead.
He moved forward. Each step, careful and deliberate, led him further into the unknown, deeper into a world where survival was a constant negotiation with danger, shadow, and instinct.
The first night had passed. The second had begun. And the real darkness—the kind that tested courage, skill, and wit—was only starting.